1. Field of the Invention
The present invention relates to a valve system of a braking device.
2. Description of Related Art
It is known that the so-called by-wire brake used as a braking device for a vehicle is provided with a pedal force simulator to generate a pedal reaction force to a brake pedal. Specifically, in the above braking device, when the by-wire brake is in a normal status, brake fluid from a master cylinder that generates fluid pressure (oil pressure) by operation of the brake pedal is fed to a pedal force simulator by shutting off a flow passage toward a brake caliper (wheel cylinder of the caliper). In the above way, a reaction force corresponding to that of a conventional brake is generated in the pedal force simulator. On the other hand, when the by-wire brake is in an abnormal status, a backup brake is actuated by shutting off the brake fluid flowing into the pedal force simulator and the brake fluid is fed to the brake caliper. Switching between feeding and shutting off the brake fluid to the pedal force simulator is performed by switching a pedal force simulator valve that is a solenoid valve provided in the flow passage of the brake fluid between the master cylinder and the pedal force simulator.
Additionally, regarding the solenoid valve used for the braking device for a vehicle, Patent Literature 1 discloses a technique of applying an initial-operation minimum-current corresponding to an actuation force required for the initial operation to a solenoid coil within the initial operation time T1 starting from a time point of starting current, application to the solenoid coil in a solenoid valve used for a vehicle brake system. In addition, the Patent Literature 1 discloses a technique of applying an operating-state holding minimum-current corresponding to an actuation force required for holding an operating state in an operating state holding time T2 thereafter